Aphanostichopathes paucispina ( Brook, 1889 )

Opresko, Dennis M., Bo, Marzia, Stein, David P., Evankow, Ann, Distel, Daniel L. & Brugler, Mercer R., 2021, Description of two new genera and two new species of antipatharian corals in the family Aphanipathidae (Cnidaria: Anthozoa: Antipatharia), Zootaxa 4966 (2), pp. 161-174 : 169-173

Aphanostichopathes paucispina ( Brook, 1889)

( Figs. 6–8 )

Cirripathes paucispina Brook, 1889: pp. 86–87 , pl. 12, fig. 6.

not Cirripathes paucispina, van Pesch, 1910: 39 ; 1914: 174–175.

Stichopathes paucispina, Opresko and Genin, 1990: 307–310 , fig. 4–5.

Diagnosis. Colonies unbranched, long and coiled at the distal end. Polypar spines up to 0.34 mm tall and abpolypar spines about two-thirds that size. Four to five rows of spines visible in lateral view, with spines 0.9–1.2 mm apart in each row; resulting density of about 2 spines per millimeter in each row. Spines with 15–25 small conical tubercles usually confined to near the apex. Polyps up to 3.4 mm in transverse diameter, arranged in a single series, with 2.5 to 4 polyps per cm.

Material Examined. Holotype: NHMUK 1873.4.26.1, locality unknown (subsample: NMNH SEM stubs 14, 15) . Other material: MCZ 90344 (syntype of Stichopathes pourtalesi Brook ) , NW Atlantic, off Santa Cruz, U.S. Virgin Islands, Blake sta. 131, 1060 m (subsample: NMNH SEM stub 305) ; USNM 82988 , NE Pacific, Opal Seamount, R / V Atlantis II , 30.5º N, 121.913º W, 1350 m, coll. L. Levin, 23 Oct. 1984 ( NMNH SEM stub 12) .

Description of holotype. Information provided by Brook (1889) indicates that the type specimen of this species consists of two pieces totaling 23 cm in length, and with a maximum stem diameter of 1.5 mm. Brook (1889) did not indicate whether either piece was coiled. The skeletal spines were reported to be short, conical, with a blunt, “slightly rugose” apex. The illustration of the spines provided by Brook (1889, Pl. 12, fig. 6) is of relatively low, eight-fold magnification; however, based on this illustration, the height of the spines can be roughly estimated to be about 0.3 mm. From the same illustration it can also be estimated that the spines within each row are 0.9 to 1.4 mm apart. Brook reported that spines were arranged in six longitudinal rows, “four of which could be seen from one aspect” and within each row they were said to be very distant, “3 to 3.5 spine lengths” apart (equivalent to 0.9–1.2 mm based on a spine height of 0.3 mm). The type specimen of S. paucispina was re-described by Opresko and Genin (1990) who found that the spines on a segment of the stem about 1 mm in diameter (excluding the spines) were up to 0.34 mm tall on the polyp side of the axis and up to 0.24 mm on the abpolypar side, similar to the size indicated by Brook’s illustration. Opresko & Genin reported up to five rows of spines visible in lateral view, and the spacing within the rows 0.86–1.14 mm (equivalent to only 2 spines per mm). The spines ( Fig. 6 A-B) were found to be covered with a variable number of small conical tubercles from the apex down the sides about two-fifths the distance to the base. Tubercles are present on both the polypar and abpolypar spines, and as many as 15–20 tubercles can be seen on the polypar spines in lateral view (including those on the distal and proximal edges). Brook did not report that the spines possessed tubercles although in his illustration there are indications that tubercles are present. It should be noted that only a small section of the holotype was available for examination with the SEM, and it is known that in species of unbranched black corals the shape of the spines and the tubercle density may vary on sections of the stem having different diameters; therefore, it cannot be assumed that the tubercle density reported here for the type remains the same on all sections of the stem.

Although Brook could not see any polyps on the type, Opresko and Genin (1990) found the dried remains of five polyps, large ones alternating with small ones. The larger polyps are 2.3–3.4 mm in transverse diameter ( Fig. 6C ) and the smaller ones 0.8–1.2 mm in transverse diameter. The density of the polyps ranged from 2.5 to 3 polyps per cm.

Remarks. Because Brook (1889) did not see any polyps on the type specimen, he questionably assigned the species to Cirrhipathes (using the incorrect spelling Cirripathes ); a genus defined by polyps being on multiple sides of the axis. Reexamination of the type revealed the presence of polyps in a single row.

Description of non-type specimens. Of the specimens assigned to this species, the one collected at Blake sta. 131 from 1060 m off the U.S. Virgin Islands (MCZ 90344, Fig. 7A ) comes closest to the type in terms of the size of the spines; the polypar spines being up to 0.33 mm tall and the abpolypar spines 0.2 mm ( Fig. 7B ). The spines shown in Figure 7B and 7C appear taller and narrower than those in the type, but this is likely due to the fact that the diameter of the stem is only 0.41mm, less than half that of the type shown in Figure 6A . This specimen shows the same wide and variable spacing of the spines and the same small number of rows (4 or 5) as in the type. It differs from the type in that the spines appear to have a slightly greater number of tubercles (around 25 per view, Fig. 7C ), however, as noted above tubercle density may vary depending on where the spines are located on the stem. The polyp density in this specimen is 3–4 per cm which is slightly greater than that in the type (2.5–3 per cm).

In the specimen collected on Opal Seamount in the northeastern Pacific ( Fig. 8 ), the polypar spines were found to be 0.28–0.32 mm tall and the abpolypar spines 0.18–0.24 mm, and about 15 distinct conical tubercles can be seen in lateral view. Five rows of spines can be seen in lateral view and the spines within each row are spaced up to 1.2 mm apart with only 2 spines per mm. The polyps are up to 2.8 mm in transverse diameter and the polyp density is 3 per cm. On a section of stem 1.8 mm in diameter the spines are distorted in shape, and some double spines are present ( Fig. 8C ).

Comparisons. Aphanostichopathes paucispina (Brook) resembles Aphanostichopathes spiessi ( Opresko & Genin, 1990) , in that both have widely spaced spines with tubercles near the apex. The major differences between the two species are in the size and shape of the spines and in the size of the polyps. In A. paucispina the spines have a more acute apex and can be up to 0.34 mm tall on a section of stem about 1 mm in diameter or larger, whereas in A. spiessi the spines are generally blunter and not more than 0.20 mm in height. The two species also differ in the relative development of the polypar and abpolypar spines. In A. paucispina the polypar spines can be up to twice as long as the abpolypar spines, but in A. spiessi they are usually equal in length, or only slightly longer on the polyp side of the axis. In terms of polyp size, the polyps in A. spiessi are usually less than 2 mm in transverse diameter whereas those in A. paucispina are up to 3.4 mm tall.

Distribution. The species is known from the North Atlantic and the NE Pacific. Specimens assigned to this species were collected at depths greater than 1000 m.

Figures

FIGURE 6. Aphanostichopathes paucispina (Brook), schizotype of NHMUK1873.4.26.1: A. section of stem; B. single spine; C. single polyp. Images from NMNH SEM stubs 14 and 15.

FIGURE 7. Aphanostichopathes paucispina (Brook), MCZ 90344: A. corallum; B. section of stem; C. single spine. B and C from NMNH SEM stub 305.

FIGURE 8. Aphanostichopathes paucispina (Brook), USNM 82988: A. section of stem 0.65 mm in diameter; B. single spine; C. section of stem 1.8 mm in diameter. Images from NMNH SEM stub 12.